Water quality under intensive banana production and extensive pastureland in tropical Mexico

The effects of intensive banana production with high mineral‐fertilizer application and of extensive pastures were compared regarding water quality in a lowland region of SE Mexico. We monitored NO$ _3^- $ , NO$ _2^- $ , and PO₄^3– concentrations in groundwater (80 m depth), subsurface water (5 m depth), and surface water (open‐ditch drainage) at monthly intervals for a one‐year period. Irrespective of the land use, the NO$ _3^- $ concentrations in all water bodies were lower than the threshold value for drinking water and aquatic life. Particularly in areas with intense banana production, the NO$ _2^- $ contents in water exceeded the safety thresholds for drinking water of 1.0 mg L^–1 (WHO, 2006) and aquatic ecosystems of 0.2 mg L^–1 (OATA, 2008). Water from pastureland showed significantly higher PO₄^3– concentration than that from the banana plantation, indicating a high risk of eutrophication. There is a need to provide recommendations for optimal time and amount of N application in commercial banana production and for limitation of P inputs in pasturelands to avoid further contamination of water bodies.     

Farmers’ unconscious incorporation of sexually-produced genotypes into the germplasm of a vegetatively-propagated crop (Oxalis tuberosa Mol.)

Clonal propagation and sexual reproduction have diametrically opposite effects on the genetic diversity of crops, permitting, respectively, the conservation of existing genotypes or the creation of new diversity. Oxalis tuberosa Mol. (“oca”) exhibits a heteromorphic self-incompatibility system and is traditionally propagated clonally but is capable of sexual reproduction. In this study we investigated the influence of sexual reproduction on the in situ genetic diversity of a vegetatively propagated crop, taking oca as a model plant. The occurrence of sexual reproduction in natural conditions and its use by farmers were studied through surveys and interviews, while the effect of sexual reproduction on the in situ genetic diversity was evaluated using microsatellite analysis. Plantlets issuing from sexual reproduction were encountered in five of the nine visited communities. The interviews indicated that six out of the nine interviewed farmers were likely, albeit unconsciously, incorporating clonal lineages issuing from sexual reproduction into their varieties. The microsatellite analysis indicated a strong effect of such incorporations on the genetic diversity of the plant varieties. Assignment tests confirmed the allogamy of oca. “Complex varieties”, made up of individuals exhibiting genetically differentiated genotypes, were most likely the result of recent crossing. Unconscious incorporation of new genotypes into the cultivated oca germplasm is therefore highly likely, raising the question of its potential occurrence in other vegetatively propagated crops. These findings could have an important effect on the adaptive potential of oca, especially in light of the genetic erosion that threatens the crop.     

EFFECTS OF CONVERTING FOREST TO AVOCADO ORCHARDS ON TOPSOIL PROPERTIES IN THE TRANS‐MEXICAN VOLCANIC SYSTEM,MEXICO

In the present work, land cover and land use changes between 2003 and 2008 were assessed in the Cupatitzio River sub‐basin located in the Trans‐Mexican Volcanic System and Balsas Depression in Mexico. The effects of land cover conversion from temperate forest to avocado orchards on soil properties were determined. Land cover and land use databases were built for the years 1975, 2003, and 2008 using available cartographic information and interpretation of panchromatic SPOT images for the year 2008. Additionally, soil sampling was carried out in 16 representative sites in the higher parts of the sub‐basin, where avocado plantation dynamics have caused important changes in areas covered by temperate forests. Results show that (i) temperate coniferous and tropical low deciduous forests were reduced at an annual rate of 0·9 per cent (1, 001 ha y⁻¹) between 1975 and 2008; (ii) cropland areas expanded at an annual rate of 0·7 per cent between 1975 and 2008, representing a growth of 553 ha y⁻¹; (iii) wet soil aggregate stability, mechanical resistance to penetration and nitrate (N‐NO₃) concentration in the topsoil layer of Andosols were significantly affected by land use conversion to avocado orchards. Other soil properties such as organic matter, interchangeable K, and available P showed degradation tendencies. These results suggest the importance of implementing strategies for mitigating the accelerated process of transformation and degradation of natural resources in the Cupatitzio River sub‐basin. The implementation of programs for deforestation reduction should be a priority in the restoration strategy. Copyright © 2012 John Wiley & Sons, Ltd.     

LAND USE CHANGES EFFECT ON FLORISTIC COMPOSITION,DIVERSITY AND SURFACE OCCUPIED BY ERICA CILIARIS AND ERICA TETRALIX HEATHLANDS OF NW SPAIN

The extent of heathland decline is well documented in countries of the north and west of Europe, not so in southern European countries. In this paper, temporal changes produced in wet heathlands of Erica ciliaris and Erica tetralix in the last 26 years in NW Spain were analysed. Thirteen wet heathlands that had been studied in 1980 were again sampled in 2006. Plant species composition, cover, diversity, surface area occupied and soil pH were analysed in each sampling site. The results obtained showed changes in the management of almost all the sampling sites and in their surrounding area, with an increase in non‐traditional practices (afforestation, repeated burning) with respect to 1980, resulting in a general decrease in the surface area occupied by these communities. A decrease of the woody cover and, as a result, an increase in the herbaceous cover was observed. Species richness did not show significant changes, but the identity of the species changed, with 73·9 per cent of the exclusive species of these communities declining or disappearing in favour of non‐exclusive species. The pH values remained within the normal ranges for these communities, although a slight decrease was recorded. It was concluded that traditional management (cutting, grazing, sporadic burning) favoured the conservation of these ecosystems, with non‐severe effects on the vegetation, and this should be noted by conservation planners. Management of the surrounding area should also be controlled to enhance preservation of these landscapes. Copyright © 2012 John Wiley & Sons, Ltd.     

Chromomycin A2 Induces Autophagy in Melanoma Cells

The present study highlights the biological effects of chromomycin A2 toward metastatic melanoma cells in culture. Besides chromomycin A2, chromomycin A3 and demethylchromomycin A2 were also identified from the extract derived from Streptomyces sp., recovered from Paracuru Beach, located in the northeast region of Brazil. The cytotoxic activity of chromomycin A2 was evaluated across a panel of human tumor cell lines, which found IC₅₀ values in the nM-range for exposures of 48 and 72 h. MALME-3M, a metastatic melanoma cell line, showed the highest sensitivity to chromomycin A2 after 48h incubation, and was chosen as a model to investigate this potent cytotoxic effect. Treatment with chromomycin A2 at 30 nM reduced cell proliferation, but had no significant effect upon cell viability. Additionally, chromomycin A2 induced accumulation of cells in G₀/G₁ phase of the cell cycle, with consequent reduction of S and G₂/M and unbalanced expression of cyclins. Chromomycin A2 treated cells depicted several cellular fragments resembling autophagosomes and increased expression of proteins LC3-A and LC3-B. Moreover, exposure to chromomycin A2 also induced the appearance of acidic vacuolar organelles in treated cells. These features combined are suggestive of the induction of autophagy promoted by chromomycin A2, a feature not previously described for chromomycins.     

Inhibition of Bacterial Quorum Sensing by Extracts from Aquatic Fungi: First Report from Marine Endophytes

In our search for quorum-sensing (QS) disrupting molecules, 75 fungal isolates were recovered from reef organisms (endophytes), saline lakes and mangrove rhizosphere. Their QS inhibitory activity was evaluated in Chromobacterium violaceum CVO26. Four strains of endophytic fungi stood out for their potent activity at concentrations from 500 to 50 μg mL⁻¹. The molecular characterization, based on the internal transcribed spacer (ITS) region sequences (ITS1, 5.8S and ITS2) between the rRNA of 18S and 28S, identified these strains as belonging to four genera: Sarocladium (LAEE06), Fusarium (LAEE13), Epicoccum (LAEE14), and Khuskia (LAEE21). Interestingly, three came from coral species and two of them came from the same organism, the coral Diploria strigosa. Metabolic profiles obtained by Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS) suggest that a combination of fungal secondary metabolites and fatty acids could be the responsible for the observed activities. The LC-HRMS analysis also revealed the presence of potentially new secondary metabolites. This is, to the best of our knowledge, the first report of QS inhibition by marine endophytic fungi.     

Fertility of a High‐Altitude Sheep Model is Compromised by Deficiencies in Both Preovulatory Follicle Development and Plasma LH Availability

At high altitude, hypoxia and/or oxidative stress may compromise fertility. This study tested the relative effect of short‐ or long‐term exposure to high‐altitude hypobaric hypoxia and oxidative stress in sheep on preovulatory follicle dynamics and gonadotrophin secretion. Thus, growth dynamics, stereidogenic function and competence to ovulate of preovulatory follicles, as well as FSH and LH availability throughout the entire oestrous cycle, were compared among sheep native from low and high altitude, and sheep newcomers to high altitude. The results indicates that short‐term exposure in sheep newcomers to high altitude has a deleterious effect on both the ovarian function (affecting preovulatory follicular development) and the pituitary function (diminishing plasma LH availability). On the other hand, there were no detected differences in the preovulatory follicular development in sheep adapted to high altitude for generations and, conversely, LH secretion was increased, which suggests an adaptive mechanism. The treatment with antioxidant agents during a relative short period for the time of folliculogenesis (approximately 1 month and a half) changed substantially the development of preovulatory follicles in short‐term exposed sheep to similar patterns than in sheep native and living to both high and low altitude. These results highlight the role of oxidative stress in the detriment of the reproductive function in individuals recently exposed to high‐altitude hypoxic environment.     

Influence of Air Pollution and Humidity on Limestone Materials Degradation in Historical Buildings Located in Cities Under Tropical Coastal Climates

Climatic changes and the increased air pollution intensify the atmospheric degradation of stone, affecting the aspect and integrity of valuable historical buildings constructed using limestone and located in tropical coastal sites. This paper analyzes limestone degradation process due to air pollution and humidity in tropical humid conditions in historical buildings located in the cities of Havana, Cuba and San Francisco de Campeche, Mexico. Havana shows higher pollution level than San Francisco de Campeche, which presents pollution levels as a consequence of a multipollutant situation along with the presence of airborne salinity. Temperature and humidity data were recorded from the walls of historical buildings in the city of Havana: the Minor Basilica and the convent of San Francisco. Changes in dry/wet cycles due to the absence of direct sun radiation as well as a high level of SO₂ allow the formation of a black crust (mainly composed of gypsum) in the lower part of the surface of the facade of the Basilica Minor in Havana; however, crusts formed in historical buildings located in San Francisco de Campeche City are mainly composed of calcium carbonate, indicating the importance of natural degradation mechanisms mainly due to dissolution in water. In the last case, the influence of water plays an important role in the development of biodegradation, which induces the formation of calcium oxalates. Caves and cracks were found in the walls of military buildings caused by water infiltration. The influence of air contamination, humidity, and construction materials determine the type of degradation that historical buildings undergo.     

Metabolic mechanisms involved in the resistance of field populations of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) to spinosad

Tuta absoluta (Meyrick) resistance to insecticides has become a significant problem in many tomato production areas in South America. New insecticides are now available for the management of this pest (i.e. spinosad), however there is scarce information about their efficacy on field populations.With the aim of determining the susceptibility of T. absoluta to spinosad we evaluated the response of second instar larvae, from five field populations (Azapa 1, Azapa 2, Lluta, Colín and Valdivia) and a laboratory reference strain (S), to a diagnostic concentration of the insecticide. We also determined the activity of the detoxifying enzymes mixed-function oxidases (MFO), glutathione-S-transferases (GST) and esterases (EST) in the same larval stage. Larval mortality in field populations was significantly lower in Azapa 1 (50.0%), Azapa 2 (44.9%), Lluta (39.9%) and Colín (53.5%) when compared to the laboratory strain (91.7%). MFO activities in field populations were between 1.8 and 4.6 times higher than those observed in the S strain, while for EST, the ratio varied from 1.7 to 14.7. The lowest ratios were observed for the GST (0.5-2.7), however, significant differences were detected for the three enzyme systems. We conclude that the evaluated mechanisms would be involved in spinosad resistance of populations of T. absoluta, presenting an increased MFO activity in all populations.